The objective of the proposed research is to establish in vitro conditions for the assembly of functionally active E. coli S30 ribosomes from percursor S16 RNA (PS16 RNA). As a step towards realizing this goal, in vitro conditions have been established for methylation of PS16 RNA. The reaction requires PS16 RNA, radioactive S-adenosyl methionine as a methyl donor, and a partially purified enzyme fraction from E. coli as a source of the methylating enzymes. Although some methylation occurs in the absence of ribosomal proteins, addition of certain S30 ribosomal proteins stimulates methylation approximately three-fold. Current experiments indicate that some S30 ribosomal proteins strongly stimulate methylation while others have no effect or may inhibit the reaction. The results indicate that methylation occurs during an intermediate stage of ribosome assembly.